Precious and contaminant metal ion removal and recovery from aqueous solutions is becoming increasingly important from both an environmental and economic perspective. Current methods to recover precious and contaminant metal ion from aqueous solutions involve the utilization of ion exchange beds. The key difficulty with using ion exchange beds is the limited availability of the internal pore spaces, as well as large pressure drops required to move fluids through the packed matrices. The present invention provides a method and device which addresses these problems.
The parent application discloses a device (system) and method for the magnetic separation of target particles (macromolecules) from a mixture. Biotin is bound to a target particle. Magnetic beads labeled with avidin or streptlavidin are mixed with the target particles. The avidin or streptlavidin binds to the biotin and the bound complex is magnetically separated from the mixture.
The invention disclosed in the parent application embodies a flow-through multi magnetic-unit device comprising a slowly rotating horizontal chamber designed for a colloidal magnetic affinity separation process. Each magnetic unit consists of an alternating current carrying solenoid surrounding the chamber, and a pair of permanent magnets located downstream from the solenoid, that rotate with the chamber. The chamber rotation simulates a low gravity environment, severely attenuating any sedimentation of non-neutrally buoyant magnetic particles as well as feed, thus promoting good particle-target contact throughout the chamber volume. The oscillating magnetic field gradient produced by the solenoid introduces translational and rotary microparticle oscillations, enhancing mixing, while the permanent magnets immobilize the targets on the chamber walls.
The present invention comprises a fully continuous, hybrid field-gradient device (system) for magnetic affinity separation having a chamber with a plurality of repeating magnetic units distributed axially along the tube. Each magnetic unit comprises a stationary alternating current solenoid that surrounds the chamber, followed by a direct current flowing, computer controlled electromagnet, placed downstream of the solenoid. The alternating current carrying solenoids impart translational and rotary oscillations to the magnetic particles, enhancing mixing. The computer-controlled electromagnets draw magnetic particles to the chamber walls, and increase their residence time in the chamber. By manipulating the on-off cycle for these electromagnets, the exiting solution can be switched between one stream that contains a negligible concentration of target bound magnetic particles and another stream that has a high concentration of the target, bond magnetic particles without interrupting the feed.
In one embodiment, the continuous, hybrid field-gradient device is used to remove cadmium ions from a cadmium sulfate solution. 1-10 xcexcm diameter anion-exchange-resin-coated magnetic particles at a concentration of about 0.5 mg particles/mL are used as the mobile solid support. The feed consists of a 10.0 mg/L cadmium sulfate solution, at a flow rate of about 25 mL/min.
In another aspect of the invention, the continuous, hybrid field-gradient device is operated as a three-stage crosscurrent cascade wherein about 45%, 58% and 63% of the entering cadmium ions are removed at each stage respectively, with stage efficiencies that vary between about 57-65%. More than about 90% of the entering cadmium ions are removed.
The continuous, hybrid field-gradient device for colloidal magnetic affinity separation can be useful in any industry wherein affinity based separations are desired such as the electroplating industry, biotechnological industry and/or nuclear industry.